As a workaround, I would suggest adding a systemd service which mounts an overlay filesystem ontop of /usr/share/polkit-1/actions/ to make this folder writable.
This bug was fixed upstream in September.
It might still take quite a while until the release, debian package, repo sync und programs actually using it so it might be worth a workaround in the meantime anyway.
Due to this: https://github.com/polkit-org/polkit/issues/130 it's not possible for apps like the gnome extension "Battery Health Charging" to add their own polkit actions in vanilla.
As a workaround, I would suggest adding a systemd service which mounts an overlay filesystem ontop of /usr/share/polkit-1/actions/ to make this folder writable.